Process-Based Farm Emission Model for Estimating Volatile Organic Compound Emission from California Dairies

摘要

This research addresses the critical need to quantify air emissions from dairies in California with the aim of developing a process-based farm emission model that can be used as a tool for estimating and predicting rates of primary air pollutants and developing effective strategies for emission mitigation. Specifically in this project, the emissions of volatile organic compounds (VOCs) from silage and dairy manure were investigated due to their importance to the air quality problems of the state. It was found that among the many VOCs emitted, alcohols (ethanol and methanol) are the predominant VOCs emitted from silage sources and volatile fatty acids (VFAs), especially acetic acid, are the major VOCs emitted from manure sources. A computer model has been developed for predicting the ethanol emission rate from silage exposed to an open air environment. The model can be used to estimate the ethanol emission rate and total emission from the silage that contain different initial ethanol concentrations and exposed to different temperatures and air velocities. Further development and testing of the emission model is needed for its application to other scenarios such as ethanol emissions during silage mixing and from deep silage layers or piles. Experimental investigations were conducted to determine the generation and emission of VFAs and alcohols from dairy manure as it undergoes microbial degradation under different conditions that are typically encountered in free stall housing and manure storages. Ethanol generation and emission from fresh manure collected in the animal housing over a 24-hour period were measured and modeled.